Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.1.8 (cholinesterase)
 12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Various 4-arylthiomethyl-2-oxo-1,3-dioxole derivatives IIIa-o were synthesized. Their hydrolysis rates by arylesterase (EC 3.1.1.2) and cholinesterase (EC 3.1.1.8) in human serum were evaluated. Some of them were not hydrolyzed by cholinesterase, but were hydrolyzed easily by arylesterase. Among the substrates, sodium 4-((5-methyl-2-oxo-1,3-dioxol-4-yl)methylthio)benzenesulfonate (IIIg) was selected for its substrate reactivity toward arylesterase and its good water solubility. In addition, neither aliesterase (EC 3.1.1.1), acetylesterase (EC 3.1.1.6) nor cholesterol esterase (EC 3.1.1.13) hydrolyzed the compound. IIIg is thus concluded to be a specific substrate for arylesterase. Our assay system for serum arylesterase using IIIg can be readily applied to an automatic analyzer in the diagnosis of liver cirrhosis.
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PMID:2-Oxo-1,3-dioxoles as specific substrates for measurement of arylesterase activity. 193 62

The structure and some functional sites of human milk bile salt activated lipase (BAL) were studied by cDNA cloning and chemical analysis of the enzyme. Eighteen cDNA clones of human BAL were identified from lactating human breast cDNA libraries in lambda gt11 and lambda gt10 with antibody and synthetic oligonucleotides as probes. The sequence of four clones was sufficient to construct a 3018-bp BAL cDNA structure. This sequence codes for an open reading frame of 742 amino acid residues. There is a putative signal sequence of 20 residues which is followed by the amino-terminal sequence of BAL, and the mature BAL contains 722 amino acid residues. The cDNA sequence also contains a 678-base 5'-untranslated sequence, a 97-base 3'-untranslated region, and a 14-base poly(A) tail. The sequence of a 1.8-kbp insert of clone G10-4A differs from that of the other cDNA in that it contains a deletion of 198 bases (1966-2163) corresponding to 66 amino acid residues. By use of BAL cDNA as probe, it was found that the major molecular species of BAL mRNA in human mammary gland HBL-100 cells had a size of 2.9 kb and two minor species had sizes of 3.8 and 5.1 kb by Northern blot analyses. The deduced BAL protein structure contains in the carboxyl-terminal region 16 repeating units of 11 amino acids each. The repeating units have the basic structure Pro-Val-Pro-Pro-Thr-Gly-Asp-Ser-Gly-Ala-Pro with only minor substitutions. The amino acid sequence of human BAL is related to that of pancreatic lysophospholipase, cholesterol esterase, cholinesterase, acetylcholinesterase, and thyroglobulin. Ten of the 14 cyanogen bromide fragments of diisopropyl fluorophosphate inhibited human milk BAL were isolated, determined for N-terminal sequences, analyzed for amino sugars, and tested for some functional properties. These chemical studies established that the active site of human milk BAL is located at serine-194, the N-glycosylation site is present at asparagine-187, the O-glycosylation region is in the 16 repeating units near the C-terminus, and the heparin binding domain is in the N-terminal region. We have also determined the location of disulfide bridges as Cys64-Cys80 and Cys246-Cys257. The cyanogen bromide cleavage and the partial sequencing of CNBr peptides also confirmed the location of methionines in the polypeptide chain as well as the deduced cDNA sequence of BAL.
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PMID:Structure of human milk bile salt activated lipase. 198 41

The histidine residue essential for the catalytic activity of pancreatic cholesterol esterase (carboxylester lipase) has been identified in this study using sequence comparison and site-specific mutagenesis techniques. In the first approach, comparison of the primary structure of rat pancreatic cholesterol esterase with that of acetylcholinesterase and cholinesterase revealed two conserved histidine residues located at positions 420 and 435. The sequence in the region around histidine 420 is quite different between the three enzymes. However, histidine 435 is located in a 22-amino acid domain that is 47% homologous with other serine esterases. Based on this sequence homology, it was hypothesized that histidine 435 is the histidine residue essential for catalytic activity of cholesterol esterase. The role of His435 in the catalytic activity of pancreatic cholesterol esterase was then studied by the site-specific mutagenesis technique. Substitution of the histidine in position 435 with glutamine, arginine, alanine, serine, or aspartic acid abolished the ability of cholesterol esterase to hydrolyze p-nitrophenyl butyrate and cholesterol [14C]oleate. In contrast, mutagenesis of the histidine residue at position 420 to glutamine had no effect on cholesterol esterase enzyme activity. The results of this study strongly suggested that histidine 435 may be a component of the catalytic triad of pancreatic cholesterol esterase.
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PMID:Site-specific mutagenesis of an essential histidine residue in pancreatic cholesterol esterase. 199 99

We report the isolation and nucleotide sequence of the cDNA for carboxyl ester lipase (CEL) from human pancreas. CEL was purified from human pancreas and microsequence analysis was performed on the amino-terminal and internal peptides. Peptide sequence was used to design oligonucleotide probes for screening a human pancreas cDNA library. Partial length cDNAs for CEL were isolated from the library, and the 5' portion of the cDNA was obtained using the anchored polymerase chain reaction. The deduced amino acid sequence indicates that mature CEL contains 722 amino acids and is synthesized with a 20 amino acid leader peptide. The amino acid sequence is rich in proline (12.2%), with 68% of the proline residues occurring within the final 25% of protein length. This is due to the occurrence of a series of proline-rich tandem repeat units near the carboxyl terminus, and accounts for the previously observed species variation in CEL size and amino acid composition. The primary sequence of CEL shows strong similarity to members of the serine esterase family, including the identical G-E-S-A-G motif at the putative active site. A striking homology also occurs between CEL and acetylcholinesterase and cholinesterase, essential enzymes of the nervous system. Proteins with cholesteryl esterase activity have been detected in extra-pancreatic tissues including liver, intestine, kidney, aorta, macrophage, and in the milk of some species (human, gorilla, cat, dog), but not others (rat, cow). To clarify the structural relationships between these various esterases and CEL, we used the CEL cDNA to study expression in pancreas and liver. CEL mRNA was abundant in pancreas of human and rat, with the human CEL mRNA approximately 300 nucleotides larger than that from rat. CEL mRNA was not detected in human adult or fetal liver, nor in rat liver. These results indicate that CEL is not synthesized in significant amounts in liver, and suggest that the cholesterol esterase activity that has been described in liver may be due to a distinct enzyme, or may be derived from pancreas, as has been proposed for the cholesterol esterase activity in intestine.
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PMID:cDNA cloning of carboxyl ester lipase from human pancreas reveals a unique proline-rich repeat unit. 206 63

The gene encoding the rat pancreatic cholesterol esterase has been isolated and characterized. Analysis of overlapping genomic clones showed that the cholesterol esterase gene spans approximately 8 kb, containing 11 exons interrupted by 10 introns. The exons ranged in size from 83 to 201 bp except for the last exon, which was 548 bp in length. A TAAATA sequence was present at -31 nucleotides from the transcriptional initiation site. A putative pancreas-specific enhancer sequence was found at -90 bp upstream from the CAP site. Although cholesterol esterase shares three domains of similarity with cholinesterase and acetylcholinesterase, these domains were found to be localized in distinct exons of the cholesterol esterase gene. The organization of the cholesterol esterase gene suggests its divergent evolution with other members of the serine esterase gene family.
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PMID:Structure of the rat pancreatic cholesterol esterase gene. 206 57

A cDNA encoding human liver carboxylesterase and its gene were isolated. Nucleotide sequence analyses of the cDNA revealed that the predicted enzyme protein consists of 567 amino acids, including 18 amino acids of a putative signal peptide. Comparison of the deduced amino acid sequences of this enzyme with those of seven other carboxylesterases in various mammalian species, together with experimental data from several other laboratories, showed that these enzymes can be classified into three groups depending on the sequences at their carboxyl terminals and the presence or absence of one exon. A human carboxylesterase gene was found to span approximately 30 kb and to have 14 small exons. Alignments of this gene with those of human cholinesterase and rat cholesterol esterase indicated insertional sites at some introns and homologous amino acid sequences around them, although these genes have different numbers of exons. Thus the results supported the conclusion that these esterases evolved from a common ancestral gene.
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PMID:Molecular cloning and characterization of a human carboxylesterase gene. 840 73

The acidic amino acid residue required for the catalytic activity of rat pancreatic cholesterol esterase has been identified in this study by sequence comparison with other serine esterases and by site-directed mutagenesis experiments. The sequence comparison studies identified 3 acidic residues in homologous domains between cholesterol esterase, acetylcholinesterase, cholinesterase, and Geotrichum candida lipase that may potentially be the catalytic acidic residue in these proteins. The role of Glu78, Asp79, and Asp320 in the catalytic activity of rat cholesterol esterase was then addressed by mutagenesis and expression of the cDNA. Results showed that replacement of Glu78 or Asp79 with alanine has no effect on the ability of the cholesterol esterase to hydrolyze the artificial water-soluble substrate p-nitrophenyl butyrate. In contrast, the Asp320-->Ala320 substitution abolished the enzyme activity of the cholesterol esterase. The specific requirement of Asp320 for optimal enzyme activity was demonstrated by substitution of the aspartic acid with glutamic acid, thus retaining the charge unit at this position. The Asp320-->Glu320 substitution resulted in an enzyme that displayed normal interaction with bile salt. However, catalytic activity of this mutagenized protein was reduced by approximately 50%. These results strongly suggested that aspartic acid 320 is an important component of the catalytic triad of pancreatic cholesterol esterase. The specific requirement of aspartic acid, instead of glutamic acid, for optimal activity is different from that of other members of the serine esterase gene family.
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PMID:Aspartic acid 320 is required for optimal activity of rat pancreatic cholesterol esterase. 841 37

The involvement of carboxylesterase, acetylcholinesterase, butyrylcholinesterase and cholesterol esterase in pharmacology and toxicology are well recognized. However, there are few papers concerning the comparative studies of these serine hydrolases in terms of molecular level. Recently, we have studied various aspects of carboxylesterases using cDNAs of carboxylesterase isozymes purified from 9 animal species and human liver microsomes, and found that there is high homology of the N-terminal amino acid sequences of the isozymes tested. On the other hand, we compared the amino acid sequences at the active site of the individual esterases and found that the sequences of all esterases tested are strictly conserved. These results strongly suggest that the esterases involved are classified into the serine hydrolase super family.
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PMID:Molecular aspects of carboxylesterase isoforms in comparison with other esterases. 859 91

Previous work has shown that acetylcholinesterase (AChE), a member of the alpha/beta-hydrolase superfamily, is stereoselectively inhibited by the four stereoisomers of isomalathion. Recent kinetic and mass spectral data demonstrated that a difference in mechanism of inactivation exists for AChE treated with (1R)- versus (1S,3S)-stereoisomers. This study sought to determine whether other alpha/beta-hydrolases are stereoselectively inhibited by isomalathion and if the difference in mechanism of AChE inactivation between (1R)- and (1S,3S)-isomers is conserved for other alpha/beta-hydrolases. Bimolecular rate constants of inhibition (k(i)) were measured for human and equine butyrylcholinesterase (HBChE and EBChE, respectively) and bovine cholesterol esterase (BCholE) with all four isomers. Isomalathion isomers inhibited these enzymes with the following order of potency: (1R,3R) > (1R,3S) > (1S,3R) > or = (1S,3S). Ratios of k(i) values for the most potent to the least potent isomer were 10.5 (HBChE), 11.9 (EBChE), and 68.6 (BCholE). Rate constants of reactivation (k(3)) were measured for enzyme inhibited by isomalathion isomers. HBChE, EBChE, and BCholE inactivated by the (1R)-isomers readily reactivated. However, enzymes modified by (1S)-isomalathions were refractory toward reactivation, and k(3) values were not significantly different from zero for HBChE and BCholE treated with the (1S,3S)-isomer. Computer-based docking experiments were performed for BCholE with (1R,3R)- and (1S,3S)-enantiomers. Calculated structures predicted a difference in primary leaving group: diethyl thiosuccinate for (1R,3R)-isomalathion and thiomethyl for the (1S,3S)-isomer. The data demonstrate that the alpha/beta-hydrolases used in this study are stereoselectively inhibited by isomalathion. Furthermore, the results suggest that the mechanistic shift demonstrated to occur for inhibition of AChE by (1R)- versus (1S,3S)-isomers is conserved for butyrylcholinesterase and cholesterol esterase.
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PMID:Probing the active sites of butyrylcholinesterase and cholesterol esterase with isomalathion: conserved stereoselective inactivation of serine hydrolases structurally related to acetylcholinesterase. 1145 26

Studies have shown that inflammatory (cholesterol esterase, CE) and salivary (pseudo-cholinesterase, PCE) enzymes can cause the breakdown of bisphenol-A diglycidyl dimethacrylate (bisGMA) and triethylene glycol dimethacrylate (TEGDMA) components from composite resins. Based on the above consideration, it was desired to show how CE- and PCE-catalyzed hydrolysis of resin components was dependent on the enzymes' concentration and to determine their distinct specificities (if any) towards resin components. Photopolymerized model composite resin samples (60% weight fraction silanated barium glass filler) based on bisGMA and TEGDMA monomers (55/45 weight ratio of the matrix, respectively) were incubated with PBS and either 0.01, 0.05, 0.1 or 1 unit/ml of CE or PCE for 16 days (pH 7.0, 37 degrees C). Incubation solutions were analyzed by high-performance liquid chromatography (HPLC), UV spectroscopy and mass spectrometry. The composite samples were characterized by scanning electron microscopy (SEM). Degradation rates of bisGMA and TEGDMA monomers were assessed. The results showed that CE had a greater specificity towards cleaving bisGMA while PCE showed a greater specificity towards TEGDMA. A strong enzyme concentration dependence was observed which suggests that the level of degradation products generated for a material will depend on the esterase make-up of an individual's saliva in combination with the specific formulation of monomer components used.
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PMID:Biodegradation of a dental composite by esterases: dependence on enzyme concentration and specificity. 1453 61


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